# 限定*的导入范围
__all__ = ['add', 'mul']


# 求和
def add(a, b):
    return a + b


# 求差
def sub(a, b):
    return a - b


# 求积
def mul(a, b):
    return a * b


# 求商
def div(a, b):
    return a / b
